I think from the title it is already clear what and how I'm going to do. I want to make a NVR on the basis of an old broken android smartphone.

#### A small background.
I have already made several versions of the video surveillance system for my house. Something worked, something not. In the course of experiments, I returned to the classic version - DVR + cameras. But here there were some nuances that I would like to eliminate.

Current task is simple - at regular intervals take pictures from the ip camera, save them on the memory card and send to ftp server. Then, on the server, using the utility motiontrack, determine the presence of movements and when they are detected, send pictures via email.
<center> ![2.jpg](https://cdn.steemitimages.com/DQmPkwMjsjE2TerfYfjf5feUb1fgCMPXXWN4jQwVE2X54An/2.jpg)</center>

But I have a video recorder from an unnamed Chinese manufacturer what can't send pictures to the ftp or on email - only videos. Unfortunately I did not find the firmware able to fix it, so instead of the DVR I used the old PC running linux. Using old PC is good solution except for one - power consumption.

I noticed daily energy consumption and came to the conclusion that video surveillance with my devices would eat about $10 per month.  It seems to be cheap, but my income for the last months rarely exceed $200, so even such a sum will be significant.  And it's not include spending on the internet.

In addition, when using a DVR or a PC, you need to take care of uninterrupted power supply - the equipment works in the village, where outages are by no means rare. This requires ups, but I do not have it.

But I have a few old android smartphones with broken screens that can be useful for my task.

![IMG_20180718_003840.jpg](https://cdn.steemitimages.com/DQma6VgSU7ykZdJodmYxjDz7iQvHYuV5ciM7Tdar54VRfZ7/IMG_20180718_003840.jpg)

Unfortunately, I did not find any application that would allow me to capture pictures from the rtsp stream of the ip camera  and at the same time might be installed and configured from the console, so I decided to implement something of my own.


#### Building FFMPEG
As you can see from the header - my decision is the console version of ffmpeg for the android.  Of course, I did not immediately come to this option. I'm not an android developer, so I was very worried about how  I will implement the rtsp client. Considering options integration ffmpeg into my application,  I came across one excellent project

https://github.com/Khang-NT/ffmpeg-binary-android.

Its author made a script for configuring and compiling ffmpeg, thanks to which even the child will be able to build FFmpeg executable binary for Android. It is enough to perform a few simple steps:

1. Download Android NDK r15 (I have old droids of version 4) https://developer.android.com/ndk/downloads/older_releases

2. Correct some params in build script ./build_ffmpeg.sh for your own needs.
In parameter  --enable-protocol='file,pipe' add rtp ( --enable-protocol='file,pipe,rtp')
next in parameter --enable-demuxer add rtsp (--enable-demuxer='rtsp,aac...)
![1.jpg](https://cdn.steemitimages.com/DQmNnuJpGz6T7cTMyjh1edrixjqGPsAsYw5aMRdoEdJSRFc/1.jpg)

3. Run the build script, installing the missing dependencies by the way.
./build_ffmpeg.sh arm lite /absolute path/build_scripts/build_dir /absolute path/build_scripts/final/arm


After about 20 minutes I got a ready-made binary. Copied it to the phone using adb - 
`adb push ./ffmpeg /storage/sdcard1/ffmpeg`

And then, using a simple command  
`adb shell '/storage/sdcard1/ffmpeg -i "rtsp://192.168.1.38:554/onvif1" -y -vframes 1 /storage/sdcard1/cam.jpg' ` made I shot from camera.

Everything worked out. 

![cam.jpg](https://cdn.steemitimages.com/DQmZNTaJbXrCDp2LJ6jYnKUAJS51kdCrNDN3SxJhSWZTYSJ/cam.jpg)

Next goal is to build th whole project - write some scripts and make some hardware manipulations  with phone, but about this in the following parts.